The present invention relates to a multi-channel flow through a turbine impeller pump assembly to cancel the radial pressure loads on the turbine impeller.
In the assembly of turbine impeller pumps, a turbine impeller, keyed to the rotating shaft, rotates within a plane perpendicular to the shaft within the confines of annular liners. As set forth in U.S. Pat. No. 5,137,418, assigned to the assignee of the present invention, the turbine impeller is axially movable with respect to the shaft, to be positioned between the annular liners. Also, such pump assemblies include a single channel flow through the annular liners to the impeller. However, this single channel flow does not compensate for the shaft radial loading caused by hydraulic forces that necessarily occurs within the pump assembly during pumping operations. Such forces cause the shaft and impeller to incur forces and moments and thus move off-center and rotate in an axial plane of the shaft centerline thereby causing interference between the rotating impeller and the stationary liners within the pump assembly unless clearance is provided. Clearance allowances for this deflection is a compromise between a design pressure limit and leakage. Increasing clearance allows more deflection without damage but leakage losses increase to the detriment of efficiency. Increasing leakage reduces the maximum capability. Such interferences caused by pressure above the designed value result in premature pump failures thereby resulting in costly and expensive repair to the pump assembly.